1. Technical Field
The present invention generally relates to an improved landing gear retraction and shock absorption system having an air over oil shock absorber wherein the oil is magneto-rheological.
2. Description of the Prior Art
Various combinations of springs and shock absorbers are known to absorb the landing energy of aircraft and provide suspension. Electric, hydraulic, or pneumatic systems have been used to extend and retract landing gear, in some cases using the shock absorbing cylinder as an actuator. Most prior art shock absorbing systems have the characteristic that high forces associated with hard or crash landings will structurally fail the shock absorbers before much energy is absorbed. As a result, the aircraft structure itself and the passengers absorb the crash forces. Other prior art designs absorb crash forces by permanently deforming a portion of the shock absorbing device.
U.S. Pat. No. 5,944,283 describes a system that utilizes the difference between the internal pressure of a shock absorber and atmospheric pressure to control flow between two internal chambers. By providing such pressure limiting means in the shock absorber, it is possible to absorb the design maximum amount of energy before structural failure, without damaging the shock absorber or the airframe.
One embodiment of an aircraft landing gear constructed in accordance with the present invention utilizes a sealed cylinder that is divided by a cylinder head to define an upper chamber and a lower chamber. The lower chamber is further divided by a piston having a piston rod passing through a sealed lower cylinder end. The cylinder head includes one or more orifices, the opening of each containing an electromagnetic coil that is configured to control the viscosity of the magneto-rheological fluid passing therethrough. The electrical current through the electromagnetic coil is continually controlled by a microcomputer with attached sensors for sensing the position of the piston and the pressure between the piston and the cylinder head. It is the pressure between the piston and the cylinder head that decelerates the aircraft evenly throughout the desired piston stroke. The pressure also is limited to a desired maximum level so that, in a severe crash, the shock absorber will absorb significant energy before it fails structurally.
Accordingly, it is an object of the present invention to provide a combined air suspension and shock absorber capable of smoothly decelerating the landing of an aircraft throughout a large range of vertical velocities.
Another object is to have pressure peak limiting means that operates during hard or crash landings, such that maximum impact energy is absorbed before the shock absorber bottoms or fails.
Yet another object of the present invention is for the air suspension to be dynamically optimized for the current weight of the aircraft.
A further object of the present invention is for the suspension and the shock absorber also to be operable as an actuator for a retractable landing gear.
Another object of the present invention is to provide a retractable landing gear actuator that can be powered with low pressure air or other gas.